Vampires and the promise of eternal youth have always been popular with teenagers. But with the extreme popularity of “Twilight,” today’s teenagers are taking a real bite out of the trend — and each other. Msnbc.com reports that some teenagers are biting each other and then licking or sucking each other’s blood. This has health officials worried.

As one teenager called “GothicGirl10” wrote on an online forum, “Having that thick, warm, copper-tasting blood in my mouth is the best thing I can think of! Sometimes my boyfriend lets me feed off him. I let him feed off me as well.” Biting puts people at risk for HIV and hepatitis infections, and 10 to 15 percent of human bites lead to infection.

Experts say the human mouth contains more bacteria than a dog’s — in fact, our mouths are teeming with more bacteria than in any other place in our bodies. In fact, as NPR reports, some people have so many bacteria in their mouth that their teeth deteriorate, creating “zombie mouth,” despite dental care.

Dr. Thomas Abshire is a pediatric blood and cancer specialist and spokesman for the American Academy of Pediatrics. Abshire says the current biting trend is more about branding and passion. As he told Msnbc.com, “If you think about it, there is such glamorization in those teen vampire movies, they make it seem so sexy and appealing and intriguing. It’s all mixed up with passion.” Other teenagers point out that they do it just for the thrill.